Question

Elution means :

• A. making the DNA bands visible under UV radiations.
• B. separation of DNA fragments on agarose gel.
• C. isolating alien DNA from the choice organism.
• D. cutting and extraction of DNA bands from the agarose gel.

Hint:

Elution is the last step after electrophoresis: the DNA band is cut out of the gel and the DNA is extracted from it.

Answer 1

The Correct Option is D

Step 1: Understand the term:
Gel electrophoresis separates cut DNA fragments into bands on an agarose gel. After that, a needed fragment has to be taken out of the gel.
The step that does this has a special name in the NCERT chapter on biotechnology.

Step 2: Recall the sequence of steps:
First the DNA is cut with restriction enzymes and run on the gel. The fragments move towards the anode because DNA is negatively charged.
Next the gel is stained with ethidium bromide and seen under UV light as orange bands.
Then the bands are cut out of the gel with a clean blade. This cutting and extraction of bands is called elution.

Step 3: Check option (A):
Making the bands visible under UV light is the job of ethidium bromide staining, not elution. So (A) is wrong.

Step 4: Check option (B):
Separation of fragments on agarose gel is gel electrophoresis itself. It happens before elution. So (B) is wrong.

Step 5: Check option (C):
Isolating alien DNA from the chosen organism is the first step of the whole procedure. It uses cell lysis and enzymes. So (C) is wrong.

Step 6: Check option (D):
Cutting out the DNA bands from the gel and extracting the DNA from them is exactly elution. The purified fragments are then used for cloning. So (D) is right.

Final Answer:
Elution means cutting out the DNA bands from the agarose gel and extracting the DNA. This is option (D). \[ \boxed{\text{(D)}} \]